Modeling hydrolysis of slowly biodegradable organic compounds in biological nutrient removal activated sludge systems

Abstract

Hydrolysis is an important process in biological wastewater treatment and is known to be the rate-limiting step in organic carbon removal from municipal or industrial wastewater. The influence of the readily biodegradable chemical oxygen demand fraction in biological wastewater treatment systems has been extensively investigated, but little is known about the effects of slowly biodegradable substrate (XS) on denitrification and enhanced biological phosphorus removal. The biodegradation of XS is initiated by hydrolysis, which is an integral part of activated sludge models, such as the Activated Sludge Model no. 2d (ASM2d). This process is slower than heterotrophic growth and thus becomes the rate-limiting step for the biodegradation of organic compounds. The aim of this study was to evaluate different concepts of modeling the hydrolysis process using the original and modified version of ASM2d. Batch test results obtained at a large biological nutrient removal (BNR) plant in Gdansk (Poland) provided an experimental database for comparison of the two model predictions. Both models were compared in terms of their predictions for the most important process rates in BNR activated sludge systems. In comparison with the orginal ASM2d, the modified model had no or only minor effect on the predicted nitrate utilization rate, phosphate release rate and anoxic/aerobic phosphate uptake rate, but better predicted the oxygen uptake rate. The average ARDs (average relative deviations) were 19.0 and 29.3% (original ASM2d) vs. 13.4 and 20.4% (modified ASM2d), respectively, for the settled wastewater without pretreatment and after coagulation-flocculation.

Computer Simulation in Predicting Biochemical Processes and Energy Balance at WWTPs

“…Sample results and model predictions of batch experiments are presented in Figure 2 a-b [4,6]. Set of the process stoichiometric and kinetic parameters in ASM2d was used as a base point of further process calibration in newly developed comprehensive model Mantis2 for simulation study of "virtual" plant layout in GPS-x (Figure 2c).…”

Potential of hydrolysis of particulate COD in extended anaerobic conditions to enhance biological phosphorous removal

“…For example, Orhon et al () modified the model of aerobic hydrolysis in ASM2d by incorporating a new variable of “readily hydrolysable pCOD.” They found that the modified model could predict more accurately the oxygen uptake rate (OUR) of activated sludge with both municipal and industrial wastewater. Drewnowski and Makinia () compared the proposed model with ASM2d for modeling a BNR activated sludge system and found the modified model, except for OUR results, could not improve the accuracy of results for anaerobic phosphorous release and anoxic/aerobic phosphorous uptake rates. Therefore, there is a critical need to further the understanding of the mechanism of hydrolysis process under anaerobic condition and to develop specific model for its kinetic estimation.…”

“…The objective of this study was to assess the effect of anaerobic hydrolysis of pCOD on phosphorous removal performance. The anaerobic hydrolysis of pCOD was mainly investigated by using kinetic tests with anaerobic condition of about 2 h (Choi and Lee, ; Drewnowski and Makinia, , ; Goel et al, ; Puig et al, ). In this study, the anaerobic HRT was extended to 4 h to assure the potential effect of pCOD under anaerobic condition, even at low level, could be evaluated.…”

Impact of optical indices on particle size distribution of activated sludge measured by laser diffraction method

“…Others investigate the relationship between the presence of protozoa in sludge and the structure and morphology of flocs on the course of the wastewater treatment process [9][10][11]. An important and currently commonly discussed tasks in wastewater treatment technology are the ways of description of physiological activity of activated [12,13] and fractioning of the substrate to build and calibrate computer models of sewage treatment systems [14][15][16][17][18]. An important aspect of investigation is also application of raw and treated sewage in agriculture [19][20][21].…”